The specs say:
Admittance shall be by means of a locked door and/or key operated switch, which in order to provide compatibility within Local Authorities, shall be a Yale Key, 10½ Section, change 900. Access to level 1 facilities shall be gained without opening the main controller door(s).
What exactly is the meaning of the bolded section? I guess it defines some kind of key (and associated lock), but how do I read it? How can I even begin searching for a lock fulfilling these specs?